555

What would you like to focus on for "555"? Here are quick options:

• 555 timer IC (electronics): pinout, modes (astable/monostable), key formulas (f ≈ 1.44/((R1+2R2)C), t_high = 0.693(R1+R2)C, t_low = 0.693R2C), example problems.
• Number 555 in math: prime factorization (3 × 5 × 37), divisors, sum of divisors, whether it’s deficient/abundant, Roman numeral (DLV).
• Something else? Let me know.

If you want, I can give a quick 5-minute crash course on the chosen topic and a practice problem.